Russian Foreign Minister Sergey Lavrov said Tuesday Moscow would not respond to London's request to explain Russia's alleged role in the poisoning of a former spy in the U.K. unless it is allowed access to the case materials.

On Monday, British Prime Minister Theresa May said it was "highly likely" that Moscow was involved in the attempted murder of a former Russian agent and his daughter and demanded an explanation by Tuesday midnight.

Russia had "nothing to do with it," Lavrov told reporters in Moscow.

"If the procedures provided by the Chemical Weapon Convention are fulfilled, I assure you that the Russian Federation will fulfill its obligations and respond to the relevant request," he added.

"According to the Chemical Weapon Convention, Great Britain had to contact a country suspected in chemical weapons use immediately, but didn't do it. At the same time, the requested party has the full right to get access to the substance in question in order to be able to carry out its own analysis of the substance."

Skripal, 66, and his daughter Yulia, 33, were admitted to a hospital after being found unconscious on a bench on March 4 in the southern English city of Salisbury.

“It is now clear that Mr. Skripal and his daughter were poisoned with a military-grade nerve agent of a type developed by Russia,” specifically from the Novichok group, May said Monday.

On Tuesday morning, Russian Senator Igor Morozov claimed Russia not only stopped the production of nerve gases, including Novichok, but had also completely destroyed all its reserves.

The incident has drawn comparisons to the fate of former KGB agent Alexander Litvinenko, who died in 2006 after drinking radioactive tea. Former KGB bodyguards identified as suspects in the murder denied any involvement.

Skripal was granted refuge in the U.K. following a spy exchange between Russia and the U.S. in 2010. He had been convicted by a Moscow military court of “high treason” after admitting to leaking information to British intelligence and was sentenced to 13 years in prison from this term he has spent six years in a Russian prison.